Abstract:
In this study, the effect of com cob biochar on the soil physico-chemical and
biological properties were investigated on a highly weathered tropical sandy
loam. The study comprised four treatments with four replicates established in
a randomized complete block design. Biochar was applied in two batches;
com cob biochar was first incorporated at rates of 10 t ha’1 (BC-10), 20 t ha'1
(BC-20), and 20 t ha'1 + triple super phosphate (BC-20+P) to study its effects
on aggregate characteristics, water retention, gas transport and pore structure
characteristics. Minimally disturbed soil samples from each of the 16 plots
were sampled from the plots treated with the first batch of biochar at a depth
of 0-20 cm. Metal core samplers were used for intact soil sampling.
Incorporation of biochar decreased the tensile strength of the large aggregates
(4—8 mm and 8-16 mm), but increased same in the smaller aggregates (1-2
mm). Soil friability and workability were significantly improved in the BC-20
and BC-20+P treatments. Soil water retention was measured within a pF range
of 1 to 6.8. Application of 20 t ha’1 led to significant increase in soil water
retention. The second batch had 50% of the first batch added to the respective
initial biochar treatments. Thus, the total biochar application rates were 15 t
ha'1 (BC-15), 30 t ha-1 (BC-30), and 30 t ha-1 + triple super phosphate (BC-
30+P). Soil samples were randomly collected from 20 different spots of the
plots treated with the second batch of biochar at 0 to 20 cm depth and the
bulked soil samples from each treatment were analyzed. Biochar amendment
resulted in a significant increase in the carbon lability index in the labile C
pools. The carbon and nitrogen pool indices, as well as carbon and nitrogen
management indices were increased with biochar amendment, especially in the
BC-30 and BC-30+P treated plots. Incorporation of biochar at 30 t ha'1 had
significant effects on soil microbial community composition, diversity and
total PLFA. Dehydrogenase and urease enzyme activities increased with the
increase of biochar application rate. In perspective, incorporation of biochar
improved the soil physical, chemical and biological quality of the soil. This
was manifested in the enhanced generic soil quality index calculated based on
the integration of all the measured properties in the soils treated with the
second batch of biochar application.
